This application is based on Japanese Patent Application Nos. 2000-306155 filed Oct. 5, 2000, and 2001-239599 filed Aug. 7, 2001, the contents of which are incorporated hereinto by reference.
1. Field of the Invention
The present invention relates to a method of modifying or treating a surface of an ophthalmic lens. More particularly, the present invention is concerned with a method of modifying the ophthalmic lens surface by irradiating the ophthalmic lens surface with plasma generated at an atmospheric pressure, for thereby improving the properties of the ophthalmic lens surface such as wettability or hydrophilicity.
2. Discussion of Related Art
For assuring a lens user of excellent wear comfort of an ophthalmic lens such as a contact lens while eliminating a feeling of discomfort during wear of the ophthalmic lens, various techniques are proposed to modify a surface of the ophthalmic lens, for thereby improving wettability of the surface of the ophthalmic lens to attain a high degree of compatibility of the lens surface with the tear fluid of the eye, and the cornea surface of the eye.
Japanese Patent No. 2846343 discloses a method of giving wettability to a surface of an oxygen permeable hard contact lens, by subjecting the contact lens to a high-frequency glow discharge treatment at a reduced pressure in an atmosphere which does not include oxygen. JP-A-3-220519 discloses a method of improving wettability of a contact lens, by first subjecting a contact lens material to a discharge treatment at a normal or reduced pressure to generate free radicals on the surface of the contact lens material, and then effecting graft polymerization of N,N-dimethylacrylamide on the surface of the contact lens material on which the free radicals are generated.
The former method described above wherein the high-frequency glow discharge treatment is effected at a reduced pressure in an atmosphere not including oxygen, however, requires steps of replacing the ambient air in a container accommodating the contact lens, with the atmosphere which does not include oxygen, and evacuating the container after the contact lens has been accommodated therein. Accordingly, the disclosed method cannot utilize the ambient air for modifying the contact lens surface, and has a low degree of working efficiency, undesirably pushing up the cost of the surface modification of the contact lens. In the latter method, the contact lens material is initially subjected to the discharge treatment, and subsequently to the graft polymerization, so that the process steps for modifying the surface of the contact lens material are more complicated than those in the former method. Further, the cost of manufacture of the contact lens is inevitably increased.
It is known that the discharge treatment (plasma treatment) described above assures a sterilizing effect as well as improved wettability. JP-A-8-156920 discloses a method of sterilizing a subject formed of a synthetic or a natural high-molecular material by a glow discharge treatment at an atmospheric pressure while the subject is interposed between the electrodes which are opposed to each other. This method attains effective sterilization with respect to bacteria and spores.
Even if the above-described sterilizing method is applied to the ophthalmic lens for simultaneously modifying and sterilizing the ophthalmic lens surface, it requires a cumbersome step of iteratively disposing the subjects (contact lenses) to be treated in a limited space defined by and between the electrodes for effecting the discharge treatment on the subjects, making it difficult to modify, in a short period of time, the surfaces of the contact lenses which are mass-produced. Further, the above-described sterilizing method may cause insufficient modification of the contact lens surfaces since the treatment is effected in the atmosphere between the electrodes. Moreover, the contact lens surfaces may not be uniformly modified due to a variation of the density of the plasma gas to which the contact lenses are exposed.
The present invention was developed in the light of the background art situations described above. It is therefore an object of the present invention to provide a method of modifying a surface of an ophthalmic lens by contacting the surface of the ophthalmic lens with plasma generated at an atmospheric pressure, wherein the ophthalmic lens surface can be uniformly modified with high degrees of working efficiency and economy without damaging the ophthalmic lens.
The object indicated above may be achieved according to a first aspect of the present invention, which provides a method of modifying a surface of an ophthalmic lens, including the steps of: generating plasma at an atmospheric pressure; and contacting the ophthalmic lens with the plasma for modifying the surface of the ophthalmic lens.
In the present method indicated above wherein the plasma is generated at an atmospheric pressure and the ophthalmic lens is brought into contact with the plasma, the surface of the ophthalmic lens can be modified so as to improve its wettability or hydrophilicity without evacuating the container in which the ophthalmic lens is accommodated, for thereby significantly improving the working efficiency while decreasing a time and a cost required for modifying the ophthalmic lens surface. Further, the present method does not require any equipment (e.g., gas conduit and working gas) for replacing the ambient air in the container with a suitable atmosphere resulting in reduction of an equipment cost.
In one preferred form of the above-indicated first aspect of the present invention, the step of contacting the ophthalmic lens with the plasma comprises a step of blowing the plasma onto the ophthalmic lens through at least one opening of a plasma control member which is spaced apart from the surface of the ophthalmic lens.
In one advantageous mode of the above preferred form of the first aspect of the invention, the plasma control member has a matrix of a multiplicity of openings. Preferably, the plasma control member is a network which has a matrix of a multiplicity of openings each having a size of 0.3xcx9c15 mm. The network is preferably a wire framework consisting of a plurality of wires each having a diameter of 0.1xcx9c3 mm. Preferably, the plasma control member is a planar member which has a matrix of a multiplicity of perforations formed through a thickness thereof. The planar member preferably has an opening ratio of 15xcx9c70%, and is a sheet member which has perforations formed by punching and which has a thickness in a range of 0.1xcx9c3 mm.
The object indicated above may be achieved according to a second aspect of the invention, which provides a method of modifying a surface of an ophthalmic lens, including the steps of: generating plasma at an atmospheric pressure between electrodes of a plasma generating device; and blowing the plasma from the plasma generating device by introducing a gas between the electrodes, so as to irradiate the ophthalmic lens located outside the plasma generating device with the plasma blown out from the plasma generating device for modifying the surface of the ophthalmic lens.
In the present method described above, the ophthalmic lens to be treated is disposed outside the electrodes of the plasma generating device, and the plasma generated at an atmospheric pressure between the electrodes is forced to be blown onto the ophthalmic lens by introducing a gas between the electrodes. This arrangement eliminates the conventionally required cumbersome step of iteratively disposing a predetermined number of ophthalmic lenses within a limited space between the electrodes, resulting in a speedy treatment of the ophthalmic lens. Accordingly, the present method assures high efficiency and economy in modifying the ophthalmic lens surface.
The present method wherein the plasma generated between the electrodes is blown onto the ophthalmic lens by the gas introduced between the electrodes is unlikely to suffer from variation in the density of plasma gas blown out from the plasma generating device, so that the ophthalmic lens surface can be uniformly modified.
In one preferred form of the above second aspect of the invention, the method further includes a step of interposing a plasma control member between the ophthalmic lens and the plasma generating device, and wherein the plasma is blown onto the ophthalmic lens through at least one opening of the plasma control member.
In this arrangement wherein the plasma generated at the atmospheric pressure is blown onto the ophthalmic lens through at least one opening of the plasma control member, portions of the plasma contact or collide with the plasma control member in the vicinity of the at least one opening before passing through the opening, whereby the plasma is blown onto the ophthalmic lens in various directions which include the direction in which the plasma is initially blown out from a suitable plasma generating device. Since the plasma which has passed through the at least one opening of the plasma control member is blown onto the ophthalmic lens in the various directions, the plasma is unlikely to concentrate on the peripheral portion (edge portion) of the ophthalmic lens, and arcs tend to generate near the plasma control member instead of the edge portion of the ophthalmic lens. Accordingly, the present method prevents the edge portion of the ophthalmic lens from suffering from a phenomenon similar to an arc discharge, for thereby effectively preventing damaging or cracking of the lens body.
In the present method wherein the plasma is generated at the atmospheric pressure between the electrodes of the plasma generating device and the ophthalmic lens is brought into contact with the plasma, the surface of the ophthalmic lens can be modified so as to improve its wettability or hydrophilicity without evacuating the container in which the ophthalmic lens is accommodated, for thereby significantly improving the working efficiency while decreasing a time and a cost required for modifying the ophthalmic lens surface. Further, the present method does not require any equipment (e.g., gas conduit and working gas) for replacing the ambient air in the container with a suitable atmosphere, resulting in reduction of an equipment cost.
In one advantageous mode of the above preferred form of the second aspect of the invention, the plasma control member has a matrix of a multiplicity of openings. Preferably, the plasma control member is a network which has a matrix of a multiplicity of openings each having a size of 0.3xcx9c15 mm. The network is preferably a wire framework consisting of a plurality of wires each having a diameter of 0.1xcx9c3 mm. Preferably, the plasma control member is a planar member which has a matrix of a multiplicity of perforations formed through a thickness thereof. The planar member preferably has an opening ratio of 15xcx9c70%, and is a sheet member which has perforations formed by punching and which has a thickness in a range of 0.1xcx9c3 mm.
In another preferred form of the above-described second aspect of the invention, the step of blowing the plasma is effected on at least one ophthalmic lens while the at least one ophthalmic lens is moved relative to the plasma generating device by a conveyor. According to this arrangement, the at least one ophthalmic lens is continuously moved or transferred by the conveyor to the position at which the surface of the ophthalmic lens is modified by the plasma blown from the plasma generating device, so that the ophthalmic lens is effectively treated by the plasma, resulting in high working efficiency and economy.
In still another preferred form of the above-described second aspect of the invention, the step of blowing the plasma is effected while the ophthalmic lens is held by a flexible lens holder. According to this arrangement, the ophthalmic lens is prevented from being blown off by the plasma or protected from deformation due to a strong flow of the plasma gas blown out from the plasma generating device, effectively protecting the ophthalmic lens from being damaged.
Preferably, the plasma is blown out from the plasma generating device in a direction which is perpendicular to an optical axis of the ophthalmic lens, so that the plasma flows laterally on the ophthalmic lens. In this arrangement, the entire surface of the ophthalmic lens, e.g., a front and a back surface of the contact lens, is irradiated with the plasma, assuring uniform surface modification of the ophthalmic lens.
Preferably, the plasma is blown onto one of opposite surfaces of the ophthalmic lens in a direction parallel to an optical axis of the ophthalmic lens. According to this arrangement, one of opposite surfaces of the ophthalmic lens, e.g., one of the front and back surfaces of the contact lens, can be entirely and uniformly irradiated with the plasma. Preferably, the plasma is blown onto opposite surfaces of the ophthalmic lens in opposite directions which are parallel to the optical axis of the ophthalmic lens. According to this arrangement, the opposite surfaces of the ophthalmic lens, e.g., both of the front and back surfaces of the contact lens, can be entirely and uniformly irradiated with the plasma.
In yet another preferred form of the second aspect of the invention, the gas introduced between the electrodes of the plasma generating device is selected from the group consisting of nitrogen, oxygen, helium, neon, argon, and mixtures thereof. Alternatively, the atmospheric air is preferably introduced between the electrodes.
Preferably, the ophthalmic lens is irradiated with the plasma for a time period in a range between 0.01 second and 180 seconds, and the ophthalmic lens is preferably a contact lens.
In a further preferred form of the second aspect of the invention, the ophthalmic lens is formed in a mold cavity defined by and between two molds of a mold assembly, and the plasma is blown on one of opposite surfaces of the ophthalmic lens while it is held by one of the two molds which have been separated away from each other, so that the one of opposite surfaces of the ophthalmic lens which has been removed from the other of the two molds is irradiated with the plasma. According to this arrangement, a desired one of opposite surfaces of the ophthalmic lens can be modified while the ophthalmic lens is held with high stability by one of the two molds.
Preferably, the plasma is generated by a glow discharge. Further, the surface of the ophthalmic lens is preferably sterilized by irradiation of the plasma. Preferably, the gas is introduced between the electrodes of the plasma generating device after the gas is in contact with hydrogen peroxide water. By using the gas which has been in contact with hydrogen peroxide water, the ophthalmic lens surface can be effectively sterilized.
The present invention is also directed to an ophthalmic lens whose surface is modified according to the methods as described above.